Earthquake-Induced Permanent Displacements of Landslides in Himalaya Using Simplified Methods and Nonlinear FE Dynamic Analysis

The paper presents a finite element (FE)-based dynamic analysis to evaluate earthquake-induced permanent displacement for a landslide in Himalaya located in Chamoli district, Uttarakhand, India. The seismic stability of slope is determined through numerical modeling using 1999 Chamoli earthquake time history. Numerically computed results are validated by comparing it with those available in the literature. In the present FE dynamic analysis, the factor of safety (FS) is considered to vary with time as yield acceleration (a(y)) depends on the excitation. This is the primary novelty of the current study. Based on the various factors, for the slope identified for this study, the numerical results are compared with those obtained using well-established sliding block and empirical methods for linear cases. Further, the effect of material nonlinearity is examined by comparing the results using linear, equivalent linear and nonlinear constitutive models. Next, the variations of permanent displacement (D) with the peak ground acceleration (PGA) and pseudostatic factor of safety (FSpseudo) are evaluated. Finally, the effect of nonlinearity on the landslide hazard index (LHI) is examined. Permanent displacement computed from FE numerical modeling is higher than the traditional sliding block method. Also, there is significant effect of nonlinearity on the permanent displacement which increases with PGA. The curves to predict permanent displacement for different constitutive models have been proposed for the local site condition which would be applicable for a similar range of material properties, geometrical properties and earthquake loading.